System and method for generating a representation of variations in elevation of friction ridges in a friction ridge pattern

ABSTRACT

A representation of variations in elevation of friction ridges in a friction ridge pattern of a subject may be generated. A sequence of images captured over a time period may be obtained. Individual images in the sequence of images may indicate areas of engagement between an imaging surface and the friction ridge pattern of the subject when the individual images are captured. Temporal information may be obtained for the individual images. The temporal information for the individual images may be used to aggregate the individual images in the sequence of images into an aggregated representation of the friction ridge pattern. The aggregation may be accomplished such that the aggregated representation depicts the areas of engagement of the friction ridge pattern with the imaging surface at different elevations of the friction ridge pattern.

FIELD OF THE DISCLOSURE

This disclosure relates to a system and a method for generating arepresentation of variations in elevation of friction ridges in afriction ridge pattern of a subject.

BACKGROUND

Fingerprints (i.e., friction ridge signatures) illustrate a pattern offriction ridges and valleys having features that may be identified. Intwo-dimensional fingerprint representations associated with existingfingerprint imaging technology, the top of the friction ridges appear tobe flat and/or planar. However, friction ridges that make up thefriction ridge pattern reflected in a fingerprint are more like mountainranges, undulating up and down with areas of lower relative elevationand areas where peaks exist. These variations are not visible in typicalfingerprints because the subject's finger is pressed against an imagingsurface causing the peaks and undulating areas to flatten such that theyare captured as if they were flat. As such, these variations inelevation are not visible as identification features.

A variety of methods for obtaining fingerprints have been developed.Because fingerprints generated by these new technologies may be matchedagainst national fingerprint databases, which were initially built fromink fingerprint cards, there has been a tendency for fingerprints to beviewed as “good” quality if the fingerprint images have a similarappearance to those of a traditional ink fingerprint. As such, whilemultiple images may be captured in some slap fingerprint capturemethods, only a single frame or image is used to identify features ofthe fingerprint, and the other images may be discarded as poor captures.Furthermore, the single frame or image used for typical fingerprintclassification is an image in which pressure is adequate to ensure thefriction ridges are compressed against the imaging surface such thatthey appear as dark ridge lines illustrating a pattern. Level Ifeatures, such as loops, arches, tents, deltas, and whorls, are mainlyused to classify or subdivide fingerprints into broad categories. LevelI features do not provide sufficient discriminating power to identifyindividuals. Level II features, such as ridge endings, bifurcations, anddots provide the basis of present day fingerprint identificationalgorithms. These features are classifications of the continuity offingerprint ridge lines. In fact, the contrast of fingerprint images isoften increased so that image processing algorithms can more accuratelyfollow ridge lines to locate deviations from ridge line continuity.Relational maps of level II features are compared to national databasesin order to identify individuals by their fingerprints.

Additional Level III features broadly arise from fine details offingerprint patterns and ridges. Typical level III details may includeridge shape, width, and path deviation, pores, incipient ridges, breaks,creases, scars, and/or a variety of ridge edge contour details. Humanexperts may use Level III features to confirm the identity of anindividual after a preliminary match based on level II features.Unfortunately, some level III features show significant variabilitywithin the same individual from fingerprints taken under differentconditions. These factors have so far raised significant challenges forthe use of level III features in automated fingerprint recognitionalgorithms.

SUMMARY

One aspect of the disclosure relates to generating a representation ofvariations in elevation of friction ridges in a friction ridge patternof a subject. A friction ridge pattern is formed by the friction ridgesof a subject and reflected in the friction ridge signature of thesubject. Various types of imaging systems and/or systems may be used tocapture the friction ridge signature of a subject. If a fingerprintscanner technology forms a two-dimensional image of the friction ridgesignature as the subject's finger (or other part of a hand) is appliedto an imaging surface, and the technology is capable of generating asequence of such images, then the technology can also be applied inaccordance with this disclosure to extract additional three dimensionaltopographical information. By way of non-limiting example, the imagingsystems may include one or more of total internal reflection basedimaging systems (i.e., TIR imaging systems), electroluminescent imagingsystems (also known as electro-optical imaging or light emittingsensors), ultrasound scanners, three-dimensional scanners, otherscanners, capacitive array imaging systems, pyro-electric (or thermal)imaging systems, radio frequency (RF) imaging systems, pressure sensorimaging systems, micro electro-mechanical devices, other optical sensorimaging systems, pressure sensitive membranes used with optical orelectrical imaging systems, and/or other systems. The imaging systemsand/or systems may capture a sequence of images. The sequence of imagesmay be analyzed to extract detailed three-dimensional topographyinformation regarding the friction ridge signature of the subject. As asubject presses their finger in contact with an imaging surface theareas of engagement between the imaging surface and the friction ridgepattern of the subject may change as time, pressure, and/or compressionof the friction ridges changes. The highest elevation portions of thefriction ridges may come into contact with the imaging surface beforethe lower portions of the friction ridges. As more pressure is appliedby the subject, the friction ridges may flatten. When performingtraditional “slap” fingerprint scans, existing technologies only use asingle final image and/or frame of the friction ridge pattern of thesubject when it is compressed and appears to comprise flat and/or planarridges and valleys. When capturing a traditional “roll” fingerprintscan, existing technologies may stitch together multiple images to forma composite image that mimics the appearance of an inked rollfingerprint. The system and/or method herein describe a sequence ofimages captured by a sensor that captures the changing amount of surfacearea of the imaging surface engaged by the friction ridge pattern asmore of the friction ridge pattern comes into contact with the imagingsurface. The sequence of images may be aggregated to create anaggregated representation of the friction ridge pattern that depicts oneor more changes in elevation of the friction ridges of the subjectand/or topography of the friction ridges and/or friction ridge patternof the subject.

The system may include one or more processors. The one or moreprocessors may be configured by machine-readable instructions. The oneor more processors may communicate with one or more imaging systems. Theimaging system(s) may include one or more of a total internal reflectionbased imaging system (i.e., TIR imaging system), a electroluminescentimaging system, a ultrasound scanner, a three-dimensional scanner, acapacitive array imaging system, thermal sensor imaging systems, radiofrequency (RF) imaging systems, pressure sensor imaging systems, otheroptical sensor imaging systems, and/or other systems. By way ofnon-limiting example, responsive to the imaging system(s) including aTIR based imaging system, the imaging system may include one or more ofa platen, a light source, a sensor, a pressure sensitive membrane,and/or other elements of imaging system(s) and/or other imaging systems.In some implementations, the system may include one or more servers.

The pressure sensitive membrane may be arranged on the imaging surface.The pressure sensitive membrane may include one or more of a topsurface, a bottom surface opposite the top surface, and/or an elasticdeformable film forming at least a portion of the top surface. Thepressure sensitive membrane may be formed such that an application ofpressure at any location on the top surface of the pressure sensitivemembrane deforms the elastic deformable film to reduce a distancebetween, and/or to increase the contact area between the deformable filmand the imaging surface at such location. In some implementations, thepressure sensitive membrane may include one or more of an elastic filmhaving a thickness between 1.5-10 μm, a light absorbing material, anelectrically conductive layer, one or more standoffs on the bottomsurface of the pressure sensitive membrane, and/or other features.

The machine-readable instructions may be configured to execute one ormore components. The components including one or more of an informationcomponent, an aggregation component, a feature identification component,and/or other components. One or more processors may be configured toobtain a sequence of images. The sequence of images may be captured overa period of time. In some implementations, the system may include asensor. The sensor may be configured to capture the sequence of images.The sequence of images may be captured over a time period. Theindividual images within the sequence of images may indicate areas ofengagement between an imaging surface and the friction ridge pattern ofthe subject when the individual images are captured.

In some implementations, the individual images in the sequence of imagesmay be captured as the areas of engagement increase over time due toincreasing compression of the friction ridge pattern on the imagingsurface. In some implementations, the individual images may be capturedas one or more areas of engagement increase and/or decrease over timedue to increasing and/or decreasing compression of one or more portionsthe friction ridge pattern on the imaging surface.

The information component may be configured to obtain temporalinformation for individual images. The temporal information may conveyrelative timing of capture for the individual images with respect tocapture of the other images. In some implementations, the temporalinformation may include timestamps. As such, the individual images inthe sequence of images may correspond to monotonically increasingtimestamp values for the sequence of images. In some implementations,the sequence of images may include sequential video frames. A quantityof images in the sequence of images may be based at least partially on aframe rate of a video including the sequential video frames.

The aggregation component may be configured to use the temporalinformation for the individual images to aggregate the individual imagesin the sequence of images into an aggregated representation of thefriction ridge pattern. The aggregation may accomplished such that theaggregated representation depicts the areas of engagement of thefriction ridge pattern with the imaging surface at different elevationsof the friction ridge pattern.

In some implementations, aggregating the sequence of images may includegenerating contours for the individual images. The contours maycorrespond to the areas of engagement of the friction ridge pattern withthe imaging surface at different elevations and/or pressure applied tothe imaging surface at different points in time over the time period. Assuch, the aggregated representation may include aggregation of thecontours for the individual images in the sequence of images. In someimplementations, aggregating the sequence of images may includegenerating gradients based on the sequence of images. The gradients maybe generated based on changes in the areas of engagement of the frictionridge pattern with the imaging surface depicted in two or more images inthe sequence of images. In some implementations, the gradients maycodify one or more slopes of one or more friction ridges.

In some implementations, the aggregated representation of the frictionridge pattern may include a representation of a topography of thefriction ridge pattern of the subject. Changes in the cross sectionalshapes of the friction ridge pattern at different elevations and/or thetemporal information may be used to determine relative elevations and/orrelative heights of one or more three dimensional features of thefriction ridge pattern of the subject. In some implementations, therelative elevation of one or more three dimensional features of thefriction ridge pattern of the subject may be determined based on thechanges in the areas of engagement between the imaging surface and thefriction ridge patter at different elevations, and/or the temporalinformation.

In some implementations, the aggregated representation of the frictionridge pattern may include a pressure distribution, a pressuredistribution map, and/or another pressure comparison.

Feature identification component may be configured to identify one ormore level-three features of the friction ridge signature of thesubject. One or more level-three features may be identified based on theaggregated representation of the friction ridge pattern. The one or morelevel-three features identified may include one or more topographicalridge peaks, topographical ridge notches, topographical ridge passes,pores, and/or other features.

Although this description primarily references friction ridge patternslocated on a human finger and/or hand, it is considered to be applicableto any place on the human body having friction ridges and/or a frictionridge pattern (e.g., such as a foot, toe, heel, palm, and/or other partsof the body).

These and other features, and characteristics of the present technology,as well as the methods of operation and functions of the relatedelements of structure and the combination of parts and economies ofmanufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limits of the invention. As usedin the specification and in the claims, the singular form of “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system configured to generate a representation ofvariations in elevation of friction ridges in a friction ridge patternof a subject, in accordance with one or more implementations.

FIG. 2 illustrates a TIR based imaging system, in accordance with one ormore implementations.

FIG. 3 illustrates a TIR based imaging system 300 with a pressuresensitive membrane 320, in accordance with one or more implementations.

FIG. 4 illustrates a sequence of images captured by a TIR-based imagingsystem having a pressure sensitive membrane, in accordance with one ormore implementations.

FIG. 5 illustrates a sequence of images captures by a TIR-based imagingsystem, in accordance with one or more implementations.

FIG. 6A illustrates a cross section of a friction ridge of a subject, inaccordance with one or more implementations.

FIG. 6B illustrates an aggregated representation for the sequence ofimages capturing the friction ridge illustrated in FIG. 6A, inaccordance with one or more implementations.

FIG. 6C illustrates an aggregated representation for the sequence ofimages capturing the friction ridge illustrated in FIG. 6A, inaccordance with one or more implementations.

FIG. 7 illustrates a method for generating a representation ofvariations in elevation of friction ridges in a friction ridge patternof a subject, in accordance with one or more implementations.

DETAILED DESCRIPTION

FIG. 1 illustrates a system 100 configured to generate a representationof variations in elevation of friction ridges in a friction ridgepattern of a subject, in accordance with one or more implementations. Afriction ridge signature (i.e., fingerprint) may include an impressionleft by the friction ridges of a human finger (e.g., the pad of a humanfinger, and/or other portions of human finger and/or hand). System 100described herein may generate a representation of variations inelevation of friction ridges in a friction ridge pattern of a subject byaggregating a sequence of images captured over time, such that multipleimages in the sequence of images may be used for a given portion of thefriction ridge pattern rather than just one.

System 100 may aggregate the individual images in the sequence of imagesinto an aggregated representation of the friction ridge pattern. Theaggregated representation may be used as a basis for identifying one ormore elevations, depths, and/or three-dimensional features of thefriction ridges of the subject. The aggregation may be accomplished suchthat the aggregated representation depicts the areas of engagement ofthe friction ridge pattern with the imaging surface at differentelevations of the friction ridge pattern. The areas of engagement of thefriction ridge pattern with the imaging surface at different elevationsmay be determined from the individual images indicating the areas ofengagement between the imaging surface and the friction ridge pattern ofthe subject when the individual images are captured. In someimplementations, the individual images may be captured as the areas ofengagement increase over time due to increasing compression of thefriction ridge pattern on the imaging surface.

Capturing a sequence of images as the subject presses their finger on animaging surface and/or as the friction ridge pattern of a subject iscompressed, may encode the history of the appearance and/ordisappearance of elevation variations and/or the three dimensionalfeatures of the topography of the friction ridges as more and morepressure is applied and the friction ridges are compressed obscuringthese elevation variations and/or three-dimensional features. Theencoded history may be reflected in the aggregated representation of thefriction ridge pattern. As such, the aggregated representation of thefriction ridge pattern may be used to identify variations in elevationand/or three dimensional features of the friction ridges of the subjectnot visible in single frame fingerprint images.

System 100 may include one or more processor(s) 124. The one or moreprocessor(s) 124 may be configured to communicate with one or moreimaging system(s) 104. One or more processor(s) 124 may be configured toexecute machine-readable instructions 105 to implement systemcomponents. The system components may include one or more of aninformation component 112, an aggregation component 114, a featureidentification component 116, and/or other components. In someimplementations, the system may include one or more server(s). Theserver(s) may be configured to communicate with one or more imagingsystem(s) 104.

In some implementations, imaging system(s) 104 may include a live scanimaging system. Imaging system(s) 104 may include one or more of a totalinternal reflection based imaging system (i.e., TIR imaging system), aelectroluminescent imaging system, a ultrasound scanner, athree-dimensional scanner, a capacitive array imaging system, thermalsensor imaging systems, radio frequency (RF) imaging systems, pressuresensor imaging systems, other optical sensor imaging systems, and/orother systems.

By way of non-limiting example, total internal reflection is a knownconcept based on light traveling at different speeds in differentmaterials. A refractive index, n_(i), of a material, i, is the speed oflight in a vacuum, c, divided by the velocity of light in the material,v_(i): n_(i)=c/v_(i). As light passes from one material to another, thechange of speed results in refraction. Measured from perpendicular tothe surface, the angle of incidence, θ₁, and the angle of refraction,θ₂, are given by Snell's law: n₁ sin(θ₁)=n₂ sin(θ₂). Accordingly, whenlight emerges from a glass block (n₁˜1.5) into air (n₂=1), the lightwill be refracted away from the perpendicular to the surface. That is,θ₂>θ₁ because n₁>n₂. At a critical angle of incidence, θ_(c), θ₂ becomes90° as the refracted light runs along the glass-air surface to form anevanescent wave. When θ₁>θ_(c), the incident light is reflected backinto the glass by a process called total internal reflection (TIR).Changes in TIR may serve to generate an image of an applied fingerprint.The intensity of light reflected from the imaging surface at aparticular location may be altered according to several opticalmechanisms. For example, changing the local effective refractive indexn₂ on or near the glass-air surface (by touching a finger or othermaterial to the glass prism) may absorb or scatter the refracted ray orthe evanescent wave.

TIR based imaging systems are generally known in the art. Such systemshave been developed to capture images of fingerprints using a prism(e.g., glass or plastic). FIG. 2 illustrates a TIR based imaging system,in accordance with one or more implementations. Light beam(s) 202 from alight source 204 is typically directed at a face of a prism at thecritical angle. Incident angles beyond the critical angle will cause thepropagating light to totally internally reflect in the prism and passout through the opposing side. When a finger is placed on imagingsurface 208 (e.g., the prism face where TIR occurs), it changes theboundary conditions such that where friction ridge(s) 210 make contactwith the prism surface, the light wave is transmitted and largelyattenuated by the skin. Where the friction ridges do not make contact(e.g., at 212), the light beam 204A is totally internally reflected bythe interface and captured by a camera or sensor 214, which may beoriented to view the surface from the reflection angle matching thesource angle of incidence. Light scattered or absorbed by the fingerreduces the local light intensity in an image captured by the camera orthe sensor 214. The result is high contrast fingerprint images from theprism surface scene such that the background appears light and afingerprint (i.e., friction ridge signature) appears dark since the TIRis frustrated by the friction ridges.

Returning to FIG. 1, image system(s) 104 may include a TIR based imagingsystem having a pressure sensitive membrane. The pressure sensitivemembrane may be arranged on the imaging surface of the TIR-based imagingsystem such that the subject presses their finger on a top surface ofthe pressure sensitive membrane. The pressure sensitive membrane mayinclude a top surface, a bottom surface opposite the top surface, and/orother portions. The pressure sensitive membrane may comprise an elasticdeformable film forming at least a portion of the top surface. Thepressure sensitive membrane may be formed such that an application ofpressure at any location on the top surface of the pressure sensitivemembrane deforms the elastic deformable film to reduce a distancebetween the deformable film and the imaging surface at such location. Insome implementations, the pressure sensitive membrane may include one ormore of: an elastic film having a thickness between 1.5-10 μm, a lightabsorbing material, an electrically conductive layer, one or morestandoffs on the bottom surface of the pressure sensitive membrane,and/or other features. In some implementations, the one or morestandoffs may be 0.2-0.5 μm high and/or 1-5 μm wide. The one or morestandoffs may be spaced 20-60 μm apart on the side of the pressuresensitive membrane closest to the imaging surface.

In some implementations, the pressure sensitive membrane may include anelectrically conductive layer. The electrically conductive layer may belocated on its lower and/or bottom surface. In some implementations,local pressure distributions from the friction ridges of the subjectthat are applied to the top surface of the pressure sensitive membranemay be converted to corresponding voltage and/or current distributionson the lower surface of the pressure sensitive membrane, which may be incontact with the imaging surface.

In some implementations, system 100 and/or imaging system(s) 104 maycomprise a pressure sensitive membrane that responds to the pressuredistribution applied from the friction ridges of the subject. Themembrane further may contain electrically active materials. As such, asensor (which may be part of imaging system 104) and detects electricalsignals from interaction with the pressure sensitive membrane, may beconfigured to capture the sequence of images characterizing pressuredistribution response of the pressure sensitive membrane over a timeperiod.

System 100 may include a sensor. In some implementations, the sensor maybe configured to capture the sequence of images. The sensor may generateand/or detect electrical signals from direct interaction with thefriction ridges of the subject. As such, the sensor may include theimaging surface in such implementations.

By way of non-limiting example, the pressure sensitive membrane may bethe same as or similar to the pressure sensitive membrane embodiments,and/or the systems and methods described in U.S. patent application Ser.No. 15/091,532, entitled “SYSTEMS AND METHODS FOR CAPTURING IMAGES USINGA PRESSURE SENSITIVE MEMBRANE,” filed Apr. 5, 2016, the foregoing beingincorporated herein by reference in its entirety.

By way of non-limiting example, FIG. 3 illustrates a TIR based imagingsystem 300 with a pressure sensitive membrane 320, in accordance withone or more implementations. The texture on the bottom surface 330 ofthe elastic film 302 may contain raised standoffs 304. Raised standoffs304 may create a thin air gap 310 between elastic film 302 and imagingsurface 322 of prism 308. Under a valley 304, air gap 310 may bemaintained. Therefore, there may be less contact between elastic film302 and imaging surface 322. When light ray 324 a travels from lightsource 312 to imaging surface 322, it may undergo total internalreflection and may be detected by the camera 314 (and/or a sensor) as alocal bright spot 328, so that valley 304 appears bright in a TIR image.A separate light ray 324 b may reach the imaging surface 322 directlyunder applied ridge pressure 306. Under applied ridge pressure 306, theelastic film 302 may be deflected towards imaging surface 322 and/or maymake more contact 326 with imaging surface 322. This contact 326 withthe index matched and light absorbing material in the elastic film 302may cause some of light ray 324 b to refract into the film and beabsorbed. Reflected light ray 326 b may have a lower intensity when itreaches camera 314 (and/or a sensor). As such, camera 314 (and/or asensor) may image regions under ridge 306 through pressure sensitivemembrane 320 as darker.

Returning to FIG. 1, in some implementations, system 100 and/or imagingsystem(s) 104 may include one or more of a platen, waveguide, and/orprism having an imaging surface. Imaging system(s) 104 may include alight source emitting a light directed toward the imaging surface.Imaging system(s) 104 may include a sensor positioned on the first oneside of the platen, waveguide, and/or prism. The sensor may beconfigured to capture the sequence of images over the time period.

By way of non-limiting example, system 100 may include one or more of aplaten, a light source, a sensor, a pressure sensitive membrane, and/orother elements of imaging system(s) 104. The platen may be a prismthrough which light beams in a TIR based imaging system are directedand/or reflected. The platen may include an imaging surface at which alight source is directed. The sensor may be positioned on a side of theplaten. The sensor may be configured to receive light reflected from theimaging surface to capture an image. The image may indicate areas ofengagement between an imaging surface and the friction ridge pattern ofthe subject when the individual images are captured. The sensor maycapture a sequence of images of the imaging surface. The sequence ofimages may be captured over a time period. In some implementations, theimaging surface may be curved and/or flexible.

The sequence of images may include multiple images capturedsequentially. In some implementations, the sequence of images mayinclude individual frames of a video. By way of non-limiting example,the sequence of images may be frames of a video captured via a TIR livescan device. Continuing the non-limiting example, a quantity of imagesin the sequence of images may be based at least partially on a framerate of the video. In some implementations, a larger quantity of imagesand/or a faster frame rate (e.g., of a video and/or camera) may lead toimages in the sequence of images being close together temporally. Afaster frame rate may improve the detail of the aggregatedrepresentation and/or the ability of the aggregated representation tomore accurately reflect the topography of the friction ridge patternbecause the image sequence will reflect much smaller time slices for thesame pressure applied.

In some implementations, imaging system 104 may include anelectroluminescent imaging system. System 100 and/or imaging system(s)104 may include one or more of an electrical voltage source or currentsource, an imaging surface, an electroluminescent layer, one or moresensors, and/or other components. The imaging surface may be configuredto receive local electrical signals from the friction ridge pattern ofthe subject responsive to the subject placing their finger on theimaging surface. The electroluminescent layer may respond to theresulting pattern of electrical signals and may emit a pattern of lightaccordingly onto a sensor. A sensor may be positioned on one side of theelectroluminescent layer. The sensor may be configured to receive lightfrom the electroluminescent layer to capture a sequence of images.

By way of non-limiting example, imaging system 104 may include acapacitance based imaging system. Imaging system 104 may characterize alocal friction ridge pattern via a sensor positioned on one side of theimaging surface. The sensor may be configured to characterize the localcapacitance and/or impedance. The sensor may be configured to capture asequence of images.

While a finger interacts with the imaging surface, a sequence of imagesmay be generated by any of the fingerprint scanning technologiesdiscussed previously. Selected mechanisms and principles by whichadditional detailed topographical information may be extracted from sucha sequence of images are described below. Within the scope of thisinvention, these same mechanisms and principles may be applied to any ofthe fingerprint scanning technologies discussed previously, which meetthe criteria of forming images of friction ridge patterns while a finger(or other hand part) interacts with an imaging surface.

As a subject presses their finger in contact with an imaging surface ofa TIR based imaging system, the areas of engagement between an imagingsurface and the friction ridge pattern of the subject may increase aspressure of the finger against the imaging surface increases, and/orcompression of the friction ridge pattern increases. In someimplementations, pressure of the finger may not be applied to theimaging surface evenly and/or a subject may readjust lifting theirfinger (decreasing pressure and compression of the friction ridgepattern. The sequence of images may include one or more images whereinone or more areas of engagement, pressure, and/or compression decreasefor a point in time. As a subject may not apply pressure evenly, it isunderstood that increasing the areas of engagement between an imagingsurface and the friction ridge pattern of the subject may indicateincreasing overall areas of engagement and/or at least a portion of thearea of engagement increases. In some implementations, the areas ofengagement may increase and/or decrease in different portions of thefriction ridge pattern.

The highest portions of the friction ridges may come into contact withthe imaging surface before the lower portions of the friction ridges.Generally, as more pressure is applied by the subject, the frictionridges may flatten. The sequence of images captured may capture thechanging amount of surface area of the imaging surface engaged by thefriction ridge pattern (e.g., the changing areas of engagement betweenan imaging surface and the friction ridge pattern of the subject) asmore of the friction ridge pattern comes into contact with the imagingsurface. The changing areas of engagement between an imaging surface andthe friction ridge pattern of the subject over time may be used tointerpolate one or more changes in elevation and/or topography of thefriction ridges of the subject.

In the typical single frame two-dimensional fingerprint known in theart, the image may be captured when the friction ridges are fullycompressed such that the friction ridges appear to be flat and/or planarridges surrounded by valleys or gaps between the ridges. Conversely, thepresent application may aggregate a sequence of images over a timeperiod. The time period may begin when the friction ridges of thesubject are at a minimal distance from the imaging surface withoutactually contacting the imaging surface. In some implementations, thetime period may begin when a minimal area of engagement (e.g., lowestamount measurable and/or discernable by system 100 and/or imaging system104, and/or at initial contact by one or more friction ridges) betweenthe imaging surface and the friction ridge pattern of the subject. Fromthe beginning of the time period to the end of the time period, thepressure applied by the subject and/or the friction ridges of thesubject may increase and/or the surface area of the imaging surfaceengaged by the friction ridge pattern of the subject may increase overtime due to increasing compression of the friction ridge pattern on theimaging surface.

FIG. 4 illustrates a sequence of images captured by a sensor having apressure sensitive membrane, in accordance with one or moreimplementations. Images 401-408 may include a sequence of imagescaptured by a TIR-based imaging system having a pressure sensitivemembrane. In some implementations, images 401-408 may include videoimages. Images 401-408 may illustrate progressively increasing pressureas a subject presses their finger (e.g., for a slap capture, etc.) on apressure sensitive membrane arranged on an imaging surface of aTIR-based imaging system. Images 401-408 may be numbered and/orpresented in sequential order in FIG. 4 based on their relative capturetime. As such, image 401 may represent an image captured before images402-408. Image 408 may be captured after images 401-407. One or more ofimages 401-408 may be the basis for and/or comprise the informationrepresenting the topography of the friction ridges of the subject fromwhich one or more level-three features may be identified. By way ofnon-limiting example, one or more topographical ridge peaks 409 may beidentifiable in image 404, image 405, and/or other images, and/or acomparison of one or more of image 404, image 405, and/or other images.Images 401-408 may depict pressure applied to a pressure sensitivemembrane arranged on the imaging surface at different points in timeover the time period during which the sequence of images are captured.In some implementations, images 401-408 may be captured as surface areaof the imaging surface engaged by the friction ridge pattern of thesubject increases over time due to increasing compression of thefriction ridge pattern on the imaging surface. Some or all of images401-408 may be aggregated into an aggregated representation of images401-408. The aggregated representation of images 401-408 may areas ofengagement and/or pressures of the friction ridge pattern at differentelevations which may be determined from individual ones of images401-408.

FIG. 5 illustrates a sequence of images captures by a sensor, inaccordance with one or more implementations. Images 501-508 may includea sequence of images captured by a TIR-based imaging system without apressure sensitive membrane. In some implementations, images 501-508 mayinclude video images. Images 501-508 may illustrated progressivelyincreasing pressuring as a subject presses their finger (e.g., for aslap capture, etc.) on an imaging surface of a TIR-based imaging system.Images 501-508 may be numbered in sequential order based on theirrelative capture time. As such, image 501 may represent the an imagecaptured before images 502-508. Image 508 may be captured after images501-507. Images 501-508 may depict the area of the imaging surfaceengaged by the friction ridge pattern of the subject at different pointsin time over the time period during which the sequence of images arecaptured. In some implementations, images 501-508 may be captured as thesurface area of the imaging surface engaged by the friction ridgepattern of the subject increases over time due to increasing compressionof the friction ridge pattern on the imaging surface. Some or all ofimages 501-508 may be the may be aggregated into an aggregatedrepresentation of images 501-508. The aggregated representation ofimages 501-508 may depict cross sectional shapes of the friction ridgepattern and/or areas of engagement between the imaging surface and thefriction ridge pattern at different elevations which may be determinedfrom individual ones of images 501-508.

Returning to FIG. 1, information component 112 may be configured toobtain the sequence of images. In some implementations, informationcomponent 112 may obtain the sequence of images from the imagingsystem(s) 104. By way of non-limiting example, the sequence of imagesmay be transmitted over a network by imaging system 104 and/or receivedat information component 112.

Information component 112 may be configured to obtain temporalinformation for individual images in the sequence of images. Thetemporal information may convey relative timing of capture for theindividual images in the sequence of images. Relative timing of capturemay describe how close to the capture of the previous image the captureof another image is, the order in which one or more images in thesequence of images were captured, the frame rate associated with thecapture of one or of more of the images in the sequence of images,and/or other information describing the relative timing of capture forthe individual images in the sequence of images. In someimplementations, the temporal information may include timestamps. Assuch, the individual images in the sequence of images may correspond tomonotonically increasing timestamp values.

Aggregation component 114 may be configured to aggregate the individualimages in the sequence of images into an aggregated representation ofthe friction ridge pattern. Aggregation component 114 may use thetemporal information for the individual images to aggregate theindividual images in the sequence of images into an aggregatedrepresentation of the friction ridge pattern. The aggregation may beaccomplished such that the aggregated representation the areas ofengagement of the friction ridge pattern with the imaging surface atdifferent elevations of the friction ridge pattern. In someimplementations, the aggregated representation may depict differentelevations and/or changes in elevation of one or more portions of thefriction ridge pattern. The different relative elevations may bedetermined from the timing of individual images of the areas ofengagement of the friction ridge pattern with the imaging surface. Insome implementations, the aggregation may represent cross sectionalshapes of the friction ridge pattern at different elevations responsiveto the sequence of images being captured as the surface area of theimaging surface engaged by the friction ridge pattern of the subjectincreased over time due to increasing compression of the friction ridgepattern on the imaging surface. The cross sectional shapes may notrepresent entirely straight and/or uniform cuts due to the subjectapplying various amounts of pressure, the imaging surface being flexibleand/or curved, and/or for other reasons.

The aggregated representation of the friction ridge pattern may includeone or more of a representation of a topography of the friction ridgesof the subject (e.g., a topographical map, etc.), a pressuredistribution, a pressure distribution map, and/or other aggregatedrepresentation of the friction ridge pattern. A topographical map mayinclude one or more contours representing the areas of engagement and/orcross sectional shapes of the friction ridge pattern at differentelevations of the friction ridge patterns.

The aggregated representation of the friction ridge pattern may includerepresentation of a topography of the friction ridge pattern of thesubject. In some implementations, aggregation component 114 may beconfigured to use changes in the areas of engagement between the imagingsurface and the friction ridge pattern at different elevations and/orthe temporal information, to determine relative elevationcharacteristics (e.g., elevations and/or heights of one or moreportions, changes in elevation and/or height, etc.) and/or reliefdetails of one or more three dimensional features of the friction ridgepattern of the subject. Such a determination of relative elevationsand/or relative heights may be used to aggregate the individual imagesin the sequence of images into the representation of the topography ofthe friction ridges of the subject. By way of non-limiting example, asone or more areas of engagement increase in size and/or changes from oneimage to the next in the sequence of images, a relative elevation may beassigned to each image. The relative elevation may indicate the areas ofengagement of the friction ridge pattern with the imaging surface atthat elevation. In some implementations, comparative image analysisand/or sequential image subtraction may be used to identify the relativeelevation associated with one or more of the images and/or for one ormore regions of the aggregated representation of the friction ridgepattern (e.g., the friction ridge signature, fingerprint, etc.).

In some implementations, aggregating the sequence of images may includegenerating contours for the individual images. The contours for theindividual images may correspond to the areas of engagement of thefriction ridge pattern with the imaging surface at different elevationsand/or pressure applied to the imaging surface at different points intime over the time period. The elevations may be determined from theindividual images of the areas of engagement at different points in timeover the time period. The elevations may include relative elevations. Byway of non-limiting example, a first image in the sequence of images maybe associated with a first timestamp indicating a first capture time inthe time period and a first elevation at the highest three-dimensionalpoint (e.g., a topographical peak and/or other high elevation) of agiven portion of a friction ridge pattern; a second image in thesequence of images may be associated with a second timestamp indicatinga second capture time after the first capture time in the time period,and a second elevation (e.g., at a second highest elevation) of thegiven portion of a friction ridge pattern; a third image in the sequenceof images may be associated with a third timestamp indicating a thirdcapture time after the second capture time in the time period, and athird elevation at a third elevation of the given friction ridge patternlower than the second elevation.

The aggregated representation may include an aggregation of the contoursfor the individual images in the sequence of images. Continuing thenon-limiting example, a first contour may be generated for the firstimage, a second contour may be generated for the second image, and/or athird contour may be generated for the third image such that theaggregated representation may include an aggregation of the firstcontour, the second contour, and/or the third contour. The aggregationof the contours for the individual images in the sequence of images mayrepresent a topographical map of the friction ridge pattern of thesubject.

By way of non-limiting example, the aggregated representation mayinclude a pressure distribution map illustrating changes in the pressuredistribution as the time period passes and/or pressure applied to apressure sensitive membrane (via more friction ridge tissue beingcompressed and/or based on the composition of the friction ridgetissue). The pressure distribution map may indicate changes in pressurefrom one image in the sequence of images to the next image in terms ofoptical grayscale values, electrical property values, or other sensoroutput levels. Areas with locally higher output signal levels and/ordarker gray scales may be assigned higher relative pressure values. Insome implementations, responsive to the aggregated representationincluding a gray scale representation of a pressure distribution map, anuphill gradient may refer to the direction in which the gray scalevalues are changing from light to dark and/or a downhill gradient mayrefer to a direction in which the gray scale values are changing fromdark to light. An uphill gradient may correlate with directions ofincreasing local applied pressure (e.g., to the pressure sensitivemembrane) and/or increasing local ridge height (e.g., corresponding toincreasing surface area of the friction ridges in contact with animaging surface over time as the subject presses their finger on animaging surface). A downhill gradient may correlate with directions ofdecreasing local applied pressure (e.g., to the pressure sensitivemembrane) and/or decreasing local ridge height (e.g., corresponding toless and/or decreasing surface area of the friction ridges in contactwith an imaging surface).

In some implementations, aggregation component 114 may be configured togenerate gradients based on the sequence of images. The gradients may begenerated based on changes in the areas of engagement of the frictionridge pattern with the imaging surface depicted in two or more images inthe sequence of images. In some implementations, sets of neighboringimages may be compared to identify changes in the areas of engagementand/or generate one or more gradients.

Areas with locally higher output signal levels and/or darker gray scalesmay correspond to one or more higher elevation portions of the frictionridges (e.g., topographical ridge peaks—due to higher elevations and/orone or more dermal papillae). By way of another non-limiting example,one or more lower elevation areas on the friction ridges of the subject(e.g., topographical ridge passes, etc.) may be indicated by locallylower output signal levels and/or lighter gray scales (e.g., one or moretopographical ridge passes that run across one or more ridges may beidentified based on lower output signals and/or lighter gray scalessurrounded by higher output signals and/or darker gray scales on twosides, depicting a lower ridge which may generally run perpendicular tothe direction of the friction ridge on which it is located).

FIGS. 6A-6C illustrate a cross section of a friction ridge of a subjectwith corresponding aggregated representations for a sequence of images,in accordance with one or more implementations. FIG. 6A illustrates across section of a friction ridge 600 of a subject, in accordance withone or more implementations. Elevations 610-650 may correspond toindividual images in a sequence of five images captured. Elevations610-650 may indicate the elevations to which the areas of engagement ofthe friction ridge pattern with the imaging surface depicted by theaggregated representation correspond. Elevation 610 may correspond to afirst image. When the first image is captured, the portions of frictionridge 600 that may be in contact with and/or engaged by the imagingsurface and/or a pressure sensitive membrane are those portions offriction ridge 600 at and/or above elevation 610. Elevation 620 maycorrespond to a second image. When the second image is captured, theportions of friction ridge 600 that may be in contact with and/orengaged by the imaging surface and/or a pressure sensitive membrane arethose portions of friction ridge 600 at and/or above elevation 620.Elevation 630 may correspond to a third image. When the third image iscaptured, the portions of friction ridge 600 that may be in contact withand/or engaged by the imaging surface and/or a pressure sensitivemembrane are those portions of friction ridge 600 at and/or aboveelevation 630. Elevation 640 may correspond to a fourth image. When thefourth image is captured, the portions of friction ridge 600 that may bein contact with and/or engaged by the imaging surface and/or a pressuresensitive membrane are those portions of friction ridge 600 at and/orabove elevation 640. Elevation 650 may correspond to a fifth image. Whenthe fifth image is captured, the portions of friction ridge 600 that maybe in contact with and/or engaged by the imaging surface and/or apressure sensitive membrane are those portions of friction ridge 600 atand/or above elevation 650.

FIG. 6B illustrates an aggregated representation for the sequence ofimages capturing friction ridge 600, in accordance with one or moreimplementations. Aggregated representation 608B includes an aggregationof contours corresponding to the cross sectional shapes of the frictionridge pattern at elevations 610-650. The first image in the sequence ofimages is associated with a first contour 601B. The second image in thesequence of images is associated with a second contour 602B. The thirdimage in the sequence of images is associated with a third contour 603B.The fourth image in the sequence of images is associated with a fourthcontour 604B. The fifth image in the sequence of images is associatedwith a fifth contour 605B. Aggregated representation 608B may representthe topography of friction ridge 600 (e.g., aggregated representation608B may be a topographical map). Aggregated representation 608B may begenerated and/or aggregated by a TIR based imaging system with orwithout a pressure sensitive membrane.

FIG. 6C illustrates an aggregated representation for the sequence ofimages capturing friction ridge 600, in accordance with one or moreimplementations. Aggregated representation 608C includes an aggregationof pressure distributions (forming a pressure map) corresponding to theareas of engagement between an imaging surface and the friction ridgepattern at elevations 610-650. The first image in the sequence of imagesis associated with a first pressure distribution 601C. The second imagein the sequence of images is associated with a second pressuredistribution 602C. The third image in the sequence of images isassociated with a third pressure distribution 603C. The fourth image inthe sequence of images is associated with a fourth pressure distribution604C. The fifth image in the sequence of images is associated with afifth pressure distribution 605C. Aggregated representation 608C mayrepresent the topography of friction ridge 600 (e.g., aggregatedrepresentation 608C may be a pressure distribution map). Aggregatedrepresentation 608C may be generated and/or aggregated by a TIR basedimaging system having a pressure sensitive membrane.

Returning to FIG. 1, feature identification component 116 may beconfigured to identify one or more level-three features of the frictionridge signature of the subject. One or more level-three features may beidentified based on the aggregated representation of the friction ridgepattern. By way of non-limiting example, these three-dimensionalfeatures may be identified in the friction ridge signature of thesubject based on information representing the topography of the frictionridges of the subject, a pressure distribution, a pressure distributionmap, and/or another aggregated representation of the friction ridgepattern. As such, aggregated representation of the friction ridgepattern may be used as a new basis for fingerprint identification. Theone or more level-three features may include one or more topographicalridge peaks, topographical ridge notches, topographical ridge passes,pores, and/or other topographical and/or three dimensional features ofthe friction ridge signature of the subject. By way of non-limitingexample, feature identification component 116 may identify twotopographical ridge peaks in individual ones of the aggregatedrepresentations illustrated in FIG. 6B and FIG. 6C.

Comparative image analysis and/or sequential image subtraction may beused to identify the relative elevation of one or more regions of theaggregated representation of the friction ridge pattern (e.g., thefriction ridge signature, fingerprint, etc.). In some implementations,the resulting point cloud data may be assembled into a 3D map (e.g., intwo dimensional form) of the fingerprint surface (e.g., informationrepresenting the topography of the friction ridge pattern), which may beanalyzed to extract level three features, and/or standard level IIfeatures.

Topographical ridge peaks may include one or more high (e.g., highelevation, etc.) points, local apexes, crests, and/or peaks of afriction ridge. An individual friction ridge may include one or moretopographical ridge peaks. A topographical ridge pass may include a pathacross a friction ridge that has a lower height and/or elevation. Insome implementations, a topographical ridge pass may include a lowerelevation pass or path between one or more topographical ridge peaks.The topographical ridge pass may vary in elevation.

A topographical notch may include one or more of an indentation, a dent,an impression, a depression, a cut out, and/or an imprint in the surfaceand/or edge of one or more friction ridges. By way of non-limitingexample, a topographical notch may include an indentation on an edge ofthe three-dimensional friction ridge. Continuing the non-limitingexample, the indentation on the edge of the friction ridge may notextend through the friction ridge uniformly. A pore may include anorifice and/or hole in a friction ridge of a subject. Pores maygenerally be known as level-three features, however pores may only bedisplayed by TIR based imaging systems when the pores are inactivebecause the moisture in active pores may cause index matching (e.g.,which makes the pore appear black, just like surrounding ridge tissue incontact with the imaging surface). In previous systems, where a singleframe is used to identify friction ridge pattern features, pores may beunreliable features. Under various amounts of pressure, a pore mayappear to be a notch and/or vice versa. Identifying level-three featuresbased on an aggregated representation of a sequence of images of thefriction ridge pattern of the subject may eliminate these issues.

Feature identification component 116 may be configured to identify oneor more level-three features of the friction ridge signature of thesubject based the aggregated representation of the friction ridgepattern captured over the time period, and/or other information. One ormore topographical ridge peaks may be identified by featureidentification component 115 based on the surface area of imagingsurface engaged by the friction ridge pattern of the subject atdifferent points in time during the process of initial contact between afinger and the imaging surface. By way of non-limiting example, thepressure applied by the finger may be increasing, and/or the distancebetween the imaging surface and the friction ridges of the subject(and/or the epidermal and/or dermal features of the finger) isdecreasing. As such, regions of the friction ridge pattern of thesubject that are higher, relative to low fingerprint valleys, may comein contact with the imaging surface first. Progressively lower regionsof the ridge may sequentially contact the imaging surface during thetime period in which the sequence of images are captured (e.g., and/orin which a video capture runs). In some implementations, aggregating theindividual images in the sequence of images into an aggregatedrepresentation of the friction ridge pattern may include methods ofcomparing sequential images to identify areas of new contact between thefinger and the imaging surface (e.g., changes in surface area of theimaging surface engaged by the friction ridge pattern of the subjectand/or changes in the areas of engagement between the imaging surfaceand the friction ridge pattern of the subject). By way of non-limitingexample, the aggregated representation of the friction ridge pattern mayinclude a reconstruction of the topography of the friction ridges basedon an assignment of a monotonically decreasing height valuecorresponding with all new pixels that became darker during thecorresponding monotonically increasing timestamp values of that sequenceof images. Other suitable methods of extracting topography from asequence of images may exist and are contemplated by the presentapplication.

Processor(s) 124, imaging system(s) 104, external resources 128, and/orother components may be operatively linked via one or more electroniccommunication links. For example, such electronic communication linksmay be established, at least in part, via a network 130 such as theInternet and/or other networks. It will be appreciated that this is notintended to be limiting, and that the scope of this disclosure includesimplementations in which processor(s) 124, imaging system(s) 104,external resources 128, and/or other components may be operativelylinked via some other communication media.

In some implementations, a given imaging system 104 may include the oneor more processor(s). External resources 128 may include sources ofinformation, hosts and/or providers outside of system 100, externalentities participating with system 100, and/or other resources.

In some implementations, processor(s) 124 is configured to provideinformation processing capabilities. As such, processor(s) 124 mayinclude one or more of a digital processor, an analog processor, adigital circuit designed to process information, an analog circuitdesigned to process information, a state machine, and/or othermechanisms for electronically processing information. Althoughprocessor(s) 124 is shown in FIG. 1 as a single entity, this is forillustrative purposes only. In some implementations, processor(s) 124may include a plurality of processing units. These processing units maybe physically located within the same device (e.g., within imagingsystem 104), or processor(s) 124 may represent processing functionalityof a plurality of devices operating in coordination. Processor(s) 124may be configured to execute components 112, 114, 116 and/or othercomponents. Processor(s) 124 may be configured to execute components112, 114, 116, and/or other components by software; hardware; firmware;some combination of software, hardware, and/or firmware; and/or othermechanisms for configuring processing capabilities on processor(s) 124.

It should be appreciated that although components 112, 114, 116 areillustrated in FIG. 1 as being co-located within a single processingunit, in implementations in which processor(s) 124 includes multipleprocessing units, one or more of components 112, 114, 116 may be locatedremotely from the other components. The description of the functionalityprovided by the different components 112, 114, 116 described below isfor illustrative purposes, and is not intended to be limiting, as any ofcomponents 112, 114, 116 may provide more or less functionality than isdescribed. For example, one or more of components 112, 114, 116 may beeliminated, and some or all of its functionality may be provided byother ones of components 112, 114, and/or 116. As another example,processor(s) 124 may be configured to execute one or more additionalcomponents that may perform some or all of the functionality attributedbelow to one of components 112, 114, 116.

FIG. 7 illustrates a method 700 for generating a representation ofvariations in elevation of friction ridges in a friction ridge patternof a subject, in accordance with one or more implementations. Theoperations of method 700 presented below are intended to beillustrative. In some implementations, method 700 may be accomplishedwith one or more additional operations not described, and/or without oneor more of the operations discussed. Additionally, the order in whichthe operations of method 700 are illustrated in FIG. 7 and describedbelow is not intended to be limiting.

In some implementations, method 700 may be implemented in one or moreprocessing devices (e.g., a digital processor, an analog processor, adigital circuit designed to process information, an analog circuitdesigned to process information, a state machine, and/or othermechanisms for electronically processing information). The one or moreprocessing devices may include one or more devices executing some or allof the operations of method 700 in response to instructions storedelectronically on an electronic storage medium. The one or moreprocessing devices may include one or more devices configured throughhardware, firmware, and/or software to be specifically designed forexecution of one or more of the operations of method 700.

At operation 702, a sequence of images captured over a time period maybe obtained. Individual images in the sequence of images may indicateareas of engagement between an imaging surface and the friction ridgepattern of the subject when the individual images are captured. Theindividual images may be captured as the areas of engagement increaseover time due to increasing compression of the friction ridge pattern onthe imaging surface. Operation 702 may be performed by an informationcomponent the same as or similar to information component 112(illustrated in FIG. 1).

At operation 704, temporal information for individual images may beobtained. The temporal information may convey relative timing of capturefor the individual images with respect to capture of the other images inthe sequence of images. Operation 704 may be performed by an informationcomponent the same as or similar to information component 112(illustrated in FIG. 1).

At operation 708, the temporal information for the individual images maybe used to aggregate the individual images in the sequence of imagesinto an aggregated representation of the friction ridge pattern. Theaggregation may be accomplished such that the aggregated representationdepicts the areas of engagement of the friction ridge pattern with theimaging surface at different elevations of the friction ridge pattern.Operation 708 may be performed by an aggregation component the same asor similar to aggregation component 114 (illustrated in FIG. 1).

Although the present technology has been described in detail for thepurpose of illustration based on what is currently considered to be themost practical and preferred implementations, it is to be understoodthat such detail is solely for that purpose and that the technology isnot limited to the disclosed implementations, but, on the contrary, isintended to cover modifications and equivalent arrangements that arewithin the spirit and scope of the appended claims. For example, it isto be understood that the present technology contemplates that, to theextent possible, one or more features of any implementation can becombined with one or more features of any other implementation.

What is claimed is:
 1. A system configured to generate a representationof variations in elevation of friction ridges, wherein a friction ridgepattern is formed from the friction ridges, the system comprising: oneor more processors configured by machine-readable instructions to:obtain a sequence of images, individual images in the sequence of imagesindicating areas of engagement between an imaging surface and thefriction ridge pattern of the subject when the individual images arecaptured, wherein the individual images are captured as the areas ofengagement increase over time due to increasing compression of thefriction ridge pattern on the imaging surface; and aggregate theindividual images in the sequence of images into an aggregatedrepresentation of the friction ridge pattern, the aggregation beingaccomplished such that the aggregated representation depicts the areasof engagement of the friction ridge pattern with the imaging surface atdifferent elevations of the friction ridge pattern, wherein theaggregated representation of the friction ridge pattern includes arepresentation of a topography of the friction ridge pattern of thesubject.
 2. The system of claim 1, further comprising: the imagingsurface, wherein the imaging surface includes a pressure sensitivemembrane arranged on the imaging surface, the pressure sensitivemembrane including a top surface, a bottom surface opposite the topsurface, and an elastic deformable film forming at least a portion ofthe top surface, the pressure sensitive membrane being formed such thatan application of pressure at any location on the top surface of thepressure sensitive membrane deforms the elastic deformable film toreduce a distance between, and/or to increase the contact area betweenthe deformable film and the imaging surface at such location.
 3. Thesystem of claim 2, wherein the pressure sensitive membrane includes oneor more of: an elastic film having a thickness between 1.5-10 μm, alight absorbing material, an electrically conductive layer, and/or oneor more standoffs on the bottom surface of the pressure sensitivemembrane.
 4. The system of claim 1, wherein the individual images and/orthe aggregated representation of the friction ridge pattern includes apressure distribution and/or a pressure distribution map.
 5. The systemof claim 1, wherein the processor is configured by machine-readableinstructions to use changes in the areas of engagement between theimaging surface and the friction ridge pattern at different to determinerelative elevation of one or more three dimensional features of thefriction ridge pattern of the subject.
 6. The system of claim 1, whereinaggregating the sequence of images includes generating contours for theindividual images, the contours corresponding to the areas of engagementof the friction ridge pattern with the imaging surface at differentelevations and/or pressure applied to the imaging surface at differentpoints in time.
 7. The system of claim 1, wherein aggregating thesequence of images includes generating gradients based on the sequenceof images, wherein the gradients are generated based on changes in theareas of engagement of the friction ridge pattern with the imagingsurface depicted in two or more images in the sequence of images.
 8. Thesystem of claim 1, wherein the sequence of images include sequentialvideo frames, and a quantity of images in the sequence of images isbased at least partially on a frame rate of a video including thesequential video frames.
 9. The system of claim 1, wherein one or moreprocessors are further configured by machine-readable instructions toidentify one or more level-three features of the friction ridgesignature of the subject based on the aggregated representation of thefriction ridge pattern, wherein the one or more level-three featuresinclude one or more topographical ridge peaks, topographical ridgenotches, and/or topographical ridge passes.
 10. The system of claim 1,further comprising: a platen, waveguide, or prism having the imagingsurface; and a light source emitting a light directed toward the imagingsurface; wherein a sensor is positioned on the first one side of theplaten, waveguide, or prism, wherein the sensor is configured to capturethe sequence of images.
 11. The system of claim 1, further comprising:an electrical voltage source or current source, wherein the imagingsurface is configured to receive local electrical signals that aregenerated by contact with the friction ridge pattern of the subject; andan electroluminescent layer responding to the electrical signals andemitting light onto a sensor, wherein the sensor is positioned on oneside of the electroluminescent layer, and wherein the sensor isconfigured to receive light from the electroluminescent layer to capturethe sequence of images.
 12. A method for generating a representation ofvariations in elevation of friction ridges, wherein a friction ridgepattern is formed from the friction ridges, the method being implementedby one or more processors configured by machine-readable instructions,the method comprising: obtaining a sequence of images, individual imagesin the sequence of images indicating areas of engagement between animaging surface and the friction ridge pattern of the subject when theindividual images are captured, wherein the individual images arecaptured as the areas of engagement increase over time due to increasingcompression of the friction ridge pattern on the imaging surface;aggregating the individual images in the sequence of images into anaggregated representation of the friction ridge pattern, the aggregationbeing accomplished such that the aggregated representation depicts theareas of engagement of the friction ridge pattern with the imagingsurface at different elevations of the friction ridge pattern, whereinthe aggregated representation of the friction ridge pattern includes arepresentation of a topography of the friction ridge pattern of thesubject.
 13. The method of claim 12, wherein the imaging surfaceincludes a pressure sensitive membrane arranged on the imaging surface,the pressure sensitive membrane including a top surface, a bottomsurface opposite the top surface, and an elastic deformable film formingat least a portion of the top surface, the pressure sensitive membranebeing formed such that an application of pressure at any location on thetop surface of the pressure sensitive membrane deforms the elasticdeformable film to reduce a distance between, and/or to increase thecontact area between the deformable film and the imaging surface at suchlocation.
 14. The method of claim 13, wherein the pressure sensitivemembrane includes one or more of: an elastic film having a thicknessbetween 1.5-10 μm, a light absorbing material, an electricallyconductive layer, and/or one or more standoffs on the bottom surface ofthe pressure sensitive membrane.
 15. The method of claim 12, wherein theindividual images and/or the aggregated representation of the frictionridge pattern includes a pressure distribution and/or a pressuredistribution map.
 16. The method of claim 12, further comprising usingchanges in the areas of engagement between the imaging surface and thefriction ridge pattern at different elevations to determine relativeelevation characteristics and/or relief details of one or more threedimensional features of the friction ridge pattern of the subject. 17.The method of claim 12, wherein aggregating the sequence of imagesincludes generating contours for the individual images, the contourscorresponding to the areas of engagement of the friction ridge patternwith the imaging surface at different elevations and/or pressure appliedto the imaging surface at different points in time.
 18. The method ofclaim 12, wherein aggregating the sequence of images includes generatinggradients based on the sequence of images, wherein the gradients aregenerated based on changes in the areas of engagement of the frictionridge pattern with the imaging surface depicted in two or more images inthe sequence of images.
 19. The method of claim 12, wherein the sequenceof images include sequential video frames, and a quantity of images inthe sequence of images is based at least partially on a frame rate of avideo including the sequential video frames.
 20. The method of claim 12,further comprising identifying one or more level-three features of thefriction ridge signature of the subject based on the aggregatedrepresentation of the friction ridge pattern, wherein the one or morelevel-three features include one or more topographical ridge peaks,topographical ridge notches, and/or topographical ridge passes.
 21. Themethod of claim 12, further comprising: receiving, by the imagingsurface, local electrical signals from the friction ridge pattern of thesubject; and responding, by an electroluminescent layer, to theelectrical signals and emitting light onto a sensor; wherein thesequence of images are captured via a sensor positioned on one side ofthe electroluminescent layer and wherein the sensor is configured toreceive light from the electroluminescent layer.
 22. The method of claim12, further comprising: characterizing, via a sensor positioned on oneside of the imaging surface and configured to characterize the localcapacitance and/or impedance, the local friction ridge pattern.